In LTE (Long Term Evolution) cellular systems, as set forth in the LTE specifications of the 3rd Generation Partnership Project (3GPP), terminals (where a terminal is referred to in LTE systems as user equipment or UE) connect to a base station (referred in LTE systems as an evolved Node B or eNB) that provides connectivity for the UE to other network entities of the LTE system that connect to an external network such as the internet. A major feature of LTE-Advanced (Long Term Evolution-Advanced or LTE-A), as part of the LTE specifications by the 3rd Generation Partnership Project (3GPP), is increased support for multi-user MIMO (multi-input multi-output) in which spatial multiplexing is used to provide separate downlink and uplink communications paths between an eNB and multiple UEs. As more UEs are scheduled per subframe for multi-user MIMO operations, the demand for physical downlink control channel (PDCCH) resources to provide scheduling for physical uplink resources is increased. The design of the PDCCH in Releases 8/9/10 of the LTE specification provides for a maximum PDCCH size of three OFDM (orthogonal frequency division multiplexing) symbols in a subframe which is inadequate for meeting this increased demand. Consequently, another control channel design, referred to as an enhanced PDCCH (EPDCCH), was introduced in Release 11 of the LTE specification.
In LTE, terminals that receive downlink data from the eNB may transmit acknowledgements (either positive or negative) back to the eNB over the physical uplink control channel (PUCCH) using an uplink resource allocated for that purpose by the eNB. In order to save signaling overhead, the current LTE specifications allow the eNB to signal the terminal what uplink resource to use for the PUCCH as a function of the structure of the information contained in the PDCCH or EPDCCH used to grant the terminal the downlink resource over which the terminal receives the downlink data that is to be acknowledged. Efficiently allocating uplink resources for the PUCCH via implicit signaling based upon the structure of the information contained in the EPDCCH is a concern of the present disclosure.